1. Field of the Invention
The present invention relates generally to a gauge assembly for use in a vehicle instrument cluster, and more particularly, to a mini gauge assembly.
2. Background and Summary of the Invention
Instrument cluster gauges, such as speedometers, tachometers, fuel and temperature gauges used in modern vehicles commonly include a pointer body or needle coupled to a permanent magnet. The magnet is generally carried in a plastic housing or bobbin, which is wrapped with two wire coils. During operation of the vehicle, current flowing through the coils creates a magnetic field, and the magnet rotates within the housing to align itself in force balance relationship with the magnetic field. Since the pointer body rotates with the magnet, positioning of the pointer body is controlled by the direction and magnitude of the current in the coils. To provide for steady movement of the pointer body, a viscous fluid is carried in the housing to damp the rotational movement of the magnet.
Current gauge assembly designs include a first inner wire coil that wraps around the bobbin in a first direction and a second outer wire coil that overlaps the first inner wire coil in a transverse direction. The inner coil is closer to the magnet mounted within the bobbin than the outer coil. Accordingly, the inner and outer coils are strategically wound to equalize the magnetic field generated by each coil. Specifically, with these gauge assemblies, the first inner wire coil is initially wound about the bobbin a first predetermined number of times and is then reverse wound a second predetermined number of times in order to reduce the field created by the first coil in order to equalize the field created by the closer inner coil and the distal outer coil. Due to the overlapping coils and the additional windings necessary to equalize the magnetic field of each coil, the size of the conventional gauge assemblies is larger than desired. Furthermore, because the coils are located far away from the magnet, the torque obtained from the conventional gauge designs is limited. Typical gauges of the above described design are disclosed in U.S. Pat. Nos. 5,219,135 and 5,631,419.
Accordingly, it is an object of the present invention to provide a gauge assembly, including a housing and a bobbin assembly including first and second bobbin elements which engage one another to define a generally cylindrical sealed chamber. An armature is supported within the chamber by a spindle which extends through an opening in one of the first and second bobbin elements. Three wire coils are wound over the bobbin assembly and are each provided with two ends each terminating at a respective terminal. The wire coils are disposed at 120.degree. angles to each other and do not overlap one another. The bobbin assembly includes three coil cavities for receiving the three wire coils. The first and second bobbin elements are identical to one another.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.